WSEGT^. 



^3 



femora.* In certain Ciirculionidse and Carabidaef the 

 parts are completely reversed in position, for the rasps are 

 seated on the interior surface of the elytra, near their 

 apices, or along their outer margins, and the edges of the 

 abdominal segments serves as the scrapers. In Pelohius 

 Hermanni (one of Dytiscidae or water-beetles) a strong 

 ridge runs parallel and near to the sutural margin of the 

 elytra and is crossed by ribs, coarse in the middle part, but 

 becoming gradually finer at both ends, especially at the 

 upper end: when this insect is held under water or in the 

 air a stridulating noise is produced by the 

 extreme horny margin of the abdomen being 

 scraped against the rasps. In a great num- 

 ber of long-horned beetles (Longicornia) the 

 organs are situated quite otherwise, the rasp 

 being on the meso-thorax, which is rubbed 

 against the pro-thorax. Landois counted 238 

 very fine ribs on the rasp of Cerambyx heros. 

 Many Lamellicorns have the power of 

 stridulating, and the organs differ greatly in 

 position. Some species stridulate very 

 loudly, so that when Mr. F. Smith caught a 

 Trox sahuloHus, a gamekeeper who stood by 

 thought he had caught a mouse; but I 

 failed to discover the proper organs in this 

 beetle. In Geotrupes and Typhceus a narrow 

 ridge runs obliquely across (r, fig. 26) the coxa 

 of each hind leg (having in G. stercorarius 84 

 ribs), which is scraped by a specially project- 

 ing part of one of the abdominal segments. 

 In the nearly allied Copris lunaris an excessively narrow 

 fine rasp runs along the sutural margin of the elytra with 

 another short rasp near the basal outer margin; but in 

 some other Coprini the rasp is seated, according to 



* Schiodte, translated in " Annals and Mag. of Nat. Hist.," vol. xx, 

 1867, p. 37. 



f Westring has described (Kroyer, " Naturhist. Tidskrift," B. ii, 

 1848-1849, p. 334) the stridulating organs in these two, as well as in 

 other families. In the Carabida? I have examined Elaphnis idigi- 

 noms and Blethisa multipunctata, sent to me bv Mr. Crotch. In 

 Blethisa the transverse ridges on the furrowed border of the abdom- 

 inal segment do not, as far as I could judge, come into play in scrap- 

 ing the rasps on the elytra. 



Fiff. 26. Hind leg 

 of Geotrupes 

 stercorarius. 

 From Landois 



r. Easp. c. Coxa. 



/. Femur, t. Tibia. 



tr. Tarsi. 



